After the invention of the light bulb, lighting devices have become ubiquitous in society. Nearly all private and public buildings and/or spaces have some form of a lighting device to provide some form of general illumination, whether it is to illuminate a room, hallway, street, roadway or the like. The number of lighting devices in the world numbers in the billions.
Since lighting devices are located in most populated areas, the lighting devices have also been used to provide functions besides lighting. For example, lighting devices have incorporated sensors such as room occupancy sensors that are used to control light, smoke detectors and/or gas detectors, such as sensors of carbon monoxide, carbon dioxide, or the like, that are used to alert persons in the vicinity of and/or remote from the lighting device of the presence of smoke and/or a harmful gas. Sensors integrated into lighting devices typically have been single purpose devices. For example, to implement occupancy sensing, smoked detection and carbon dioxide sensing in one lighting device might involve installation of three different types of sensors for the different purposes in one lighting device.
One sensing device that may be used to analyze multiple chemicals simultaneously is a hyperspectral imager. A hyperspectral imager may be a charge-coupled device (CCD) image sensor, a complimentary metal-oxide-semiconductor (CMOS) image sensor, or imaging cameras, such as a scanning camera, forward-looking infrared (FLIR) camera, or the like. The hyperspectral imager is configured to detect the intensity of light over a continuous portion of an electromagnetic spectrum.
The hyperspectral imager may output an image in which each pixel includes information detected by the image sensor derived from all wavelengths within the continuous portion of the electromagnetic spectrum being imaged. The hyperspectral imager outputs data that when presented on a display device is an image representative of the “spectrum” of a scene or object being imaged.
In contrast, multispectral imaging typically refers to imaging specific, non-contiguous bands of the electromagnetic spectrum. As a result, the multispectral image does not provide a “continuous spectrum” of a scene or object, but, instead provides an object's spectral contribution to the specific band being imaged.
While digital cameras typically use red, green, and blue visible light filters when producing an image, a hyperspectral imager has a broader spectral resolution than a common digital camera. New imaging technology is enabling the hyperspectral imager to be drastically reduced in price and size. Hyperspectral imagers previously cost tens of thousands of dollars and were large. The smallest of these hyperspectral imagers could only fit on top of a desk. However, in recent years, hyperspectral imagers have become small enough to fit in a person's hand.